Re: [PATCH v5] x86/vmx: add hvm functions to get/set non-register state

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.04.2022 05:46, Tian, Kevin wrote:
>> From: Lengyel, Tamas <tamas.lengyel@xxxxxxxxx>
>> Sent: Friday, March 25, 2022 9:33 PM
>>
>> During VM forking and resetting a failed vmentry has been observed due
>> to the guest non-register state going out-of-sync with the guest register
>> state. For example, a VM fork reset right after a STI instruction can trigger
>> the failed entry. This is due to the guest non-register state not being saved
>> from the parent VM, thus the reset operation only copies the register state.
>>
>> Fix this by adding a new pair of hvm functions to get/set the guest
>> non-register state so that the overall vCPU state remains in sync.
>>
>> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
> 
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
with ...

>> @@ -863,6 +892,17 @@ static inline void hvm_set_reg(struct vcpu *v,
>> unsigned int reg, uint64_t val)
>>      ASSERT_UNREACHABLE();
>>  }
>>
>> +static inline void hvm_get_nonreg_state(struct vcpu *v,
>> +                                        struct hvm_vcpu_nonreg_state *nrs)
>> +{
>> +    ASSERT_UNREACHABLE();
>> +}
>> +static inline void hvm_set_nonreg_state(struct vcpu *v,
>> +                                        struct hvm_vcpu_nonreg_state *nrs)
>> +{
>> +    ASSERT_UNREACHABLE();
>> +}

... these unnecessary stubs dropped (they should be introduced only
once actually needed, i.e. when a caller appears in a file which is
also built when !CONFIG_HVM), and ...

>> --- a/xen/arch/x86/mm/mem_sharing.c
>> +++ b/xen/arch/x86/mm/mem_sharing.c
>> @@ -1643,6 +1643,13 @@ static int bring_up_vcpus(struct domain *cd,
>> struct domain *d)
>>      return 0;
>>  }
>>
>> +static void copy_vcpu_nonreg_state(struct vcpu *d_vcpu, struct vcpu
>> *cd_vcpu)
>> +{
>> +    struct hvm_vcpu_nonreg_state nrs = {};
>> +    hvm_get_nonreg_state(d_vcpu, &nrs);

... this missing blank line inserted between these two lines. I'll
make both adjustments while committing.

Jan